Heat exchangers

ABSTRACT

A heat exchanger includes a body made of polymer, a plurality of first flow channels defined in the body, and a plurality of second flow channels defined in the body. The second flow channels fluidly isolated from the first flow channels. The first flow channels and second flow channels are arranged in a checkerboard pattern.

BACKGROUND

1. Field

The present disclosure relates to heat exchangers, more specifically tomore thermally efficient heat exchangers.

2. Description of Related Art

Conventional multi-layer sandwich cores are constructed out of flatsheet metal dividing plates, spacing bars, and two dimensional thincorrugated fins brazed together. The fabrication process is wellestablished and relatively simple. However, the manufacturing simplicityhas a negative impact on the performance and limits the ability tocontrol thermal efficiency.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved heat exchangers. The present disclosure providesa solution for this need.

SUMMARY

A heat exchanger includes a body made of polymer, a plurality of firstflow channels defined in the body, and a plurality of second flowchannels defined in the body. The second flow channels fluidly isolatedfrom the first flow channels. The first flow channels and second flowchannels are arranged in a checkerboard pattern.

The first and/or second flow channels can include a changing flow areaalong a length of the body. The changing flow area can increase a firstflow area toward a first flow outlet of the heat exchanger. The changingflow area can decrease a second flow area toward the first flow outletas the first flow area increases.

The first and/or second flow channels can include a changing flow areashape. The changing flow area shape can include a first polygonal flowarea at a first flow inlet which transitions to a second polygonal flowarea having more sides at a first flow outlet. The changing flow areashape can include a first polygonal flow area at a second flow inletwhich transitions to a second polygonal flow area having more sides at asecond flow outlet.

The hot and second flow channels can include a rhombus shape such thatall surfaces form primary heat transfer surfaces wherein each surfaceincludes a hot side defining a portion of a first flow channel and acold side defining a portion of a second flow channel. In certainembodiments, the first and/or second flow channels can include at leastone of a hexagonal shape or an octagonal shape. In certain embodiments,the first and/or second flow channels can include a rectilinear shape, apolygonal shape, or any other suitable shape.

In accordance with at least one aspect of this disclosure, A method formanufacturing a heat exchanger can include forming a body out of polymerto include a plurality of first flow channels and a plurality of secondflow channels such that the second flow channels are fluidly isolatedfrom the first flow channels, and such that the first flow channels andsecond flow channels are arranged in a checkerboard pattern. Forming theheat exchanger can include additively manufacturing the heat exchanger.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1A is a perspective view of an embodiment of a heat exchanger inaccordance with this disclosure, showing a hot flow inlet/cold flowoutlet of the heat exchanger;

FIG. 1B is a perspective cross-sectional view of the heat exchanger ofFIG. 1A, showing a middle portion of the heat exchanger;

FIG. 1C is a perspective cross-sectional view of the heat exchanger ofFIG. 1A, showing a hot flow outlet/cold flow inlet of the heatexchanger;

FIG. 1D is a scaled up view of a portion of the heat exchanger of FIG.1A;

FIG. 2 is a cross-sectional view of an embodiment of a heat exchanger inaccordance with this disclosure;

FIG. 3 is a cross-sectional view of an embodiment of a heat exchanger,illustrating a primary surface heat conduction and secondary surfaceheat conduction in a non-checkerboard pattern embodiment; and

FIG. 4 is a cross-sectional view of an embodiment of a heat exchanger inaccordance with this disclosure, illustrating only primary surface heatconduction as there are no secondary surfaces.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, an illustrative view of an embodiment of a heat exchanger inaccordance with the disclosure is shown in FIG. 1A and is designatedgenerally by reference character 100. Other embodiments and/or aspectsof this disclosure are shown in FIGS. 1B-4. The systems and methodsdescribed herein can be used to reduce weight and/or increaseperformance of heat transfer systems.

Referring to FIG. 1A, a heat exchanger 100 includes a body 101, aplurality of first flow channels, e.g., hot flow channels 103 asdescribed herein, defined in the body 101, and a plurality of secondflow channels, e.g., cold flow channels 105 defined in the body 101.While hot flow channels 103 and the cold flow channels 105 are describedwith respect to a relative temperature of flow therein, it iscontemplated that the hot flow channels 103 can be used for cold flowand vice versa, or any other suitable arrangement.

The cold flow channels 105 are fluidly isolated from the hot flowchannels 103. At least one of the hot flow channels 103 or the cold flowchannels 105 can include a changing characteristic along a length of thebody 101. However, it is contemplated that the flow channels 103, 105can have constant characteristics along the length of the body 101.

The hot flow channels 103 and the cold flow channels 105 can be utilizedin a counter-flow arrangement such that cold flow and hot flow arerouted through the heat exchanger 100 in opposing directions. Also, asshown, the hot flow channels 103 and the cold flow channels can bearranged such that hot and cold channels 103, 105 alternate (e.g., in acheckerboard pattern as shown).

The flow channel 103, 105 can include shapes such as one or more ofrhombuses, hexagons, and octagons. However, while the flow channels 103,105 are shown as polygons, the shapes need not be polygonal orrectilinear. As appreciated by those skilled in the art, polygonalshapes can be described using the four parameters as described below. InFIG. 1D, the four parameters are shown. As shown, the full width A andheight B are always greater than zero. The secondary width C and heightD can be zero up to the full width and height. If C>0 and D>0, the shapeis an octagon, if C>0 and D=0 (or C=0 and D>0), the shape is a hexagon,and if C=0 and D=0, the shape is a rhombus.

Any other suitable flow area shapes for the hot flow channels 103 and/orthe cold flow channels 105 are contemplated herein. For example, asshown in FIG. 2, a heat exchanger 200 can include elliptical flowchannels 203 and/or non-elliptical flow channels 205 (e.g., roundedcross shaped) defined in body 201.

As shown in FIGS. 1A, 1B, and 1C, one or more flow channels 103, 105 caninclude changing characteristics. The changing characteristics caninclude a changing flow area. For example, the changing flow area canincrease a hot flow area toward a hot flow outlet of the heat exchanger100 (e.g., as shown in transitioning from FIG. 1A, through FIG. 1B, toFIG. 1C). Similarly, the changing flow area can decrease a cold flowarea toward the hot flow outlet as the hot flow area increases (whichmay be a function of the increasing hot flow area in order to maintaintotal area of the body 101). It is contemplated that one or more of thehot flow channels 103 or the cold flow channels 105 may maintain aconstant flow area or change in any other suitable manner.

In certain embodiments, the changing characteristic of the hot and/orcold flow channels 103, 105 can include a changing flow area shape. Incertain embodiments, the changing flow area shape can include a firstpolygonal flow area at a hot flow inlet (e.g., a rhombus as shown inFIGS. 1A and 1B) which transitions to a second polygonal flow areahaving more sides at a hot flow outlet (e.g., a hexagon as shown in FIG.3). Also as shown, the changing flow area shape can include a firstpolygonal flow area at a cold flow inlet (e.g., a rhombus as shown inFIGS. 1C and 1B) which transitions to a second polygonal flow areahaving more sides at a cold flow outlet (e.g., a hexagon as shown inFIG. 1A). Any other suitable changing shape along a length of the body101 is contemplated herein (e.g., any desired change of A, B, C, and/orD as shown in FIG. 1D).

The body 101 can be made of metal and/or any other suitable material.For example, the body 101 can be made of a polymer (e.g., plastic) orother suitable insulator material. One having ordinary skill in the artwould not endeavor to use polymer as most polymers are consideredthermal insulators, and, thus, the use of polymer is counter-intuitivefor heat exchanger material. However, due to a reduction and/orelimination of secondary surfaces (e.g., surfaces where heat must travelthrough more material than the thickness of the walls) as describedbelow, polymer can be utilized, especially in thin-walled applications,because the conduction path through the polymer (e.g., plastic) is veryshort in certain embodiments of the disclosure.

For example, referring to FIG. 3, an embodiment of a body 301 is shownhaving a non-checkered scheme (e.g., a planar alignment scheme as istypical in plate-fin heat exchangers). As can be seen, primary heatconduction path (a) flows across the thickness of only two walls fromhot channels 303 to cold channels 305. Secondary heat conduction path(b) travels a much longer path through the material of body 301, whichcauses an efficiency loss. However, referring to FIG. 4, the hot andcold flow channels 103, 105 can include a suitable shape (e.g., arhombus shape as shown) such that all surfaces form primary heattransfer surfaces wherein each surface includes a hot side defining aportion of a hot flow channel 103 and a cold side defining a portion ofa cold flow channel 105. It is contemplated that other shapes (e.g., asdescribed above) can be used with a polymer body 101, however, theminimizing secondary heat transfer surfaces can improve the thermalefficiency.

It is contemplated that the heat exchanger 100 can include any suitableheader (not shown) configured to connect the hot flow channels 103 to ahot flow source (not shown) while isolating the hot flow channels 103from the cold flow channels 105. The header may be formed monolithicallywith the body 101 of the heat exchanger 100 or otherwise suitablyattached to cause the hot flow channels 103 to converge together and/orto cause the cold flow channels 105 to converge together.

In accordance with at least one aspect of this disclosure, a method formanufacturing a heat exchanger 100 includes forming a body 101 toinclude a plurality of hot flow channels 103 and a plurality of coldflow channels such that the cold flow channels 105 are fluidly isolatedfrom the hot flow channels 103, and such that at least one of the hotflow channels 103 or the cold flow channels 105 have a changingcharacteristic along a length of the body 101. Forming the heatexchanger 100 can include additively manufacturing the heat exchanger100 using any suitable method (e.g., powder bed fusion, electron beammelting, polymer deposition).

Embodiments of this disclosure can allow maximization of primary surfacearea for heat exchange while allowing flexibility to increase ordecrease the ratio of hot side to cold side flow area. Being able tochange the relative amount of flow area on each side of the heatexchanger is necessary to fully utilize the pressure drop available oneach side. Embodiments as described above allow for enhanced control offlow therethrough, a reduction of pressure drop, control of thermalstresses, easier integration with a system, and reduced volume andweight. Unlike conventional multi-layer sandwich cores, embodiments asdescribed above allow for channel size adjustment for better impedancematch across the core.

Further, in additively manufactured embodiments, since the core (e.g.,body 101) can be made out of a monolithic material, the material can bedistributed to optimize heat exchange and minimize structural stresses,thus minimizing the weight. Bending stresses generated by high pressuredifference between cold and hot side are greatly reduced by adjustingcurvature of the walls and appropriately sized corner fillets. Suchsolution reduces weight, stress, and material usage since the materialdistribution can be optimized and since the material works in tensioninstead of bending.

As described above, the certain embodiments can be additivelymanufactured (e.g., printed) as one piece out of polymer. Polymer as aheat exchanger material can offer a significant weight and cost benefit,and the drawbacks of using polymer (e.g., due to low thermalconductivity) can be significantly reduced through improving the heatconduction path (e.g., via the checkerboard pattern/reduction ofsecondary heat transfer surfaces of flow channels 103, 105 as describedabove). Hence, the conductive resistance of certain embodiments, eventhough made out of polymer, has negligible effect on performance andallows dramatic weight and cost savings. The resistance through aprimary surface made of polymer will generally be smaller than theconvective resistance between the walls and fluids so that the thermalconductivity of the polymer has little impact on the overall performanceof the heat exchanger.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for heat exchangers with superiorproperties including reduced weight and/or increased efficiency. Whilethe apparatus and methods of the subject disclosure have been shown anddescribed with reference to embodiments, those skilled in the art willreadily appreciate that changes and/or modifications may be made theretowithout departing from the spirit and scope of the subject disclosure.

What is claimed is:
 1. A heat exchanger, comprising: a body made ofpolymer; a plurality of first flow channels defined in the body; and aplurality of second flow channels defined in the body, the second flowchannels fluidly isolated from the first flow channels, wherein thefirst flow channels and second flow channels are arranged in acheckerboard pattern.
 2. The heat exchanger of claim 1, wherein thefirst and/or second flow channels can include a changing flow area alonga length of the body.
 3. The heat exchanger of claim 2, wherein thechanging flow area increases a first flow area toward a first flowoutlet of the heat exchanger.
 4. The heat exchanger of claim 3, whereinthe changing flow area decreases a second flow area toward the firstflow outlet as the first flow area increases.
 5. The heat exchanger ofclaim 2, wherein the first and/or second flow channels include achanging flow area shape.
 6. The heat exchanger of claim 5, wherein thechanging flow area shape includes a first polygonal flow area at a firstflow inlet which transitions to a second polygonal flow area having moresides at a first flow outlet.
 7. The heat exchanger of claim 5, whereinthe changing flow area shape includes a first polygonal flow area at asecond flow inlet which transitions to a second polygonal flow areahaving more sides at a second flow outlet.
 8. The heat exchanger ofclaim 1, wherein the hot and second flow channels include a rhombusshape such that all surfaces form primary heat transfer surfaces whereineach surface includes a hot side defining a portion of a first flowchannel and a cold side defining a portion of a second flow channel. 9.The heat exchanger of claim 1, wherein the first and/or second flowchannels include at least one of a hexagonal shape or an octagonalshape.
 10. The heat exchanger of claim 1, wherein the first and/orsecond flow channels include a rectilinear shape.
 11. The heat exchangerof claim 1, wherein the first and/or second flow channels include apolygonal shape.
 12. A method for manufacturing a heat exchanger,comprising; forming a body out of polymer to include a plurality offirst flow channels and a plurality of second flow channels such thatthe second flow channels are fluidly isolated from the first flowchannels, and such that the first flow channels and second flow channelsare arranged in a checkerboard pattern.
 13. The method of claim 12,wherein forming the heat exchanger includes additively manufacturing theheat exchanger.